Frozen pizzas seamlessly move from one conveyor to another.
In high-speed bakeries, a thousand — sometimes even tens of thousands — of things can go wrong at any given minute. That’s no exaggeration, especially in some of the nation’s largest and most automated cookie facilities where a little snap, crackle or pop of a belt creates a waterfall of products tumbling to the floor.
Sometimes a little jogging — where the belt slips, grabs and moves — causes a cascade of crackers, creating a mess. And listen carefully for grinding, rattling, squeaking or other slight signs that the conveyor and its belt need tweaking.
“Maintenance is the key to minimizing vibration on a belt conveyor,” noted Rick Spiak, vice-president of sales and marketing, Wire Belt Co. of America. “You want to avoid chatter or jogging of the belt because it starts bouncing things around, and it can knock things out of the lane or out of sequence.”
Typically, poor conveyor and belt design, inadequate electrical controls or lack of proper sanitation all can cause unwanted vibration.
Sanitary designed conveyors come with fewer parts, bent plate frames and sloped surfaces to enhance food safety.
“Today, manufacturers have made great improvements in all three areas,” said Peter White, president, IJ White Systems. “For instance, there have been significant improvements in PLC controls having real-time feedback from motors and belt-tensioning monitoring. New belt designs and wear strip materials with a lower co-efficient of friction can contribute to reducing vibration. Automatic cleaning systems, better sanitation and maintenance practices also have been major factors to producing smoother running conveyors.”
Enhanced belt design — specifically positive-driven belts developed over the past few years — has resulted in fewer bumps and bounces that can knock products out of whack, said Barry Whitman, global sales manager for Precision Food Division that includes Kofab and Meyer Industries.
“Instead of using a friction-drive belt that needs to wrap around a pulley creating tension to drive the belt, now there is this newer technology,” he said. “It’s a belt that has the teeth moulded to the bottom side of the belt, so it’s operating with a pulley or sprocket that’s positively engaging with those teeth to pull the belt around rather than relying on friction.”
Achraf Elhassouni, global spiral product manager, Intralox, noted that overly high tension may cause belt stretching, link fatigue and premature belt failure in conventional friction-driven spiral conveyors. If not properly dialed in, the drum in some spirals may run significantly faster than the belt to manage the belt tension, resulting in product misalignment across both the width and the length of the belt. Vibrations, Mr. Elhassouni noted, also may lead to product distortion and yield loss.
Replacing threaded nuts and sprockets with a single-slotted apparatus makes cleaning conveyors much easier.
Additionally, he said, Intralox’s DirectDrive eliminates high tension in spiral belting using the patented load reduction zone. Positively engaging the belt to the drum structure greatly enhances product alignment.
“This, in turn, results in significant service life gains and improved line efficiencies,” Mr. Elhassouni said.
Ashworth offers its PosiDrive Spiral to keep the belt moving evenly, said Jonathan Lasecki, chief engineer, Ashworth.
“We minimized as much vibration as possible in the belt, which keeps the product moving in a regimented fashion and makes the chance of it getting damaged or broken virtually limited,” he said. “The product heading into packaging is the same as the product heading out of the oven.”
In addition to identifying snagging transfer points, bakers need to pay attention to small, terminal rollers and longer pitch belts. Mr. Lasecki noted the PosiDrive’s 1-inch pitch belt provides fairly small transfer rollers to minimize the chordal action of the belt as it travels around those terminal rollers.
“We can keep the product running smoothly without that stop-and-start stutter that sometimes happens with larger terminal rollers,” he said.
Both belt and drive conveyors play a role in the amount of vibration, suggested John Kuhnz, vice-president, engineered solutions, Dorner Mfg. Corp. Modular conveyor belts have built-in tolerances over their width and length, and as the speed of the belt increases, so too will the vibration.
“One way to reduce this vibration is to install a solid slider bedplate on the frame,” Mr. Kuhnz said. “Not only will it lower the vibration from gaps in the wear strips, (the bedplate is) also completely supported, making it ideal for fragile product applications.”
